Can't see the rest of the actions in there. You want to make sure it's between the move to the other drive and the sort into subfolder. If you have this split up where you have the folder on the other drive added to Hazel and it does the sort in a separate step, there should be a natural delay already in place though. If you turn off that rule, you might want to see how long it takes until Spotlight indexes it. If it's more than a couple seconds, I'd also look into why Spotlight is so slow on that drive.